Tricarbocyanine dyestuff and method of preparation



Patented Dec. 7, 1943 TBIGARBOCYANINE DYESTUFF AND METHOD or PREPARATION John David Kendall, Ilford, England, assignor to Ilford Limited, Ilford, England, a British como n wii Ap li Februa 21, 194.0. Serial No."820 ,'22 1. In Great Britain March 21,

' 11 Claims. (01.260-240) This invention relates to the production of dyestufis 'for sensitising photographic silver halide emulsions.

It i an object of this invention to produce a new range of tricarbocyanine dyestuffs having a sensitising action on silver halide photographic emulsions and the invention includes the process for the production of the new dyestuffs, the new dyestuffs themselves and light-sensitive silver halide photographic emulsions containing the new dyestuffs.

According to the invention, tricarbocyanine dyestuffs are produced by reacting, in the pres! ence of a solvent and an acid binding agent, a quaternary salt of a thiazole or selenazole compound containing a reactive methyl group in the a position to the heterocyclic nitrogen atom with a compound obtainable by acetalising, w-PYIOIIB with an alkyl-ortho-formate.

The product obtained by acetalising -pyrone is believed to be diformyl-acetone-hexa-alkylacetal of the formula (R) 2.CH.CH2.C(OR1) 2.CH2.CH(OR1) 2 (compare the paper by Willstater and Rummerer, Berichte 38, 1470) and it is believed that the reaction with the thiazole or selenazole compound according to the invention proceeds in accordance with the following general equation:

In the foregoing formula R represents, an alkyl group, e. g. a methyl, ethyl, propyl or higher alkyl group or an aralkyl group, e. g. a benzyl group, R1 represents an alkyl group, Y represents' the negative radical of an acid, e. g. chloride, bromide, iodide, p-toluene-sulphonate, chlorate, sulphate and nitrate, and X constitutes the atoms necessary to complete a thiazole or selenazole nucleus.

A monocyclic thiazole or selenazole compound may be employed, but it is preferable to employ polycyclic thiazoles and selenazoles, e. g. benzthiazole, naphthathiazole, anthrathiazole, benzselenazole, napthaselenazole and anthraselenazole.

In the production of the 'y-pyrone derivative, various alkyl orthoiormates may be used, e. g. methyl, ethyl and propyl orthoformates.

In carrying out the reaction a single compound, such as pyridine, may be employed which is both a solvent and an acid binding agent, but it is preferred to employ a mixture of a solvent, such as ethyl alcohol, with an acid binding agent, such as sodium'acetate. In general, the r act on c e qu t smoot ly with on y e tle heating and indeed it is undesirable to heat for a prolonged period or at too high a temperature as such treatment may cause a breakdown of the reagents or of the product produced.

The new dyestufis. are valuable photographic sensitising dyestuffs for the far-red and infrared portions of the spectrum.

The following examples illustrate the invention:

Example I 1.49 gms. of l-methylbenzthiazole and 2.00 gms. of ethyl-p-toluene sulph'onate were mixed together and fused at -.1' 5;0 C. for 3 hours. The mixture was then dissolved in 50 cos. of pyridine and 5.8- gms. of diformyl-acetone-hexaethyl-acetal added to the hot solution. Themix ture was then refluxed for about five minutes, during which period a strong green. colour appeared. The mixture was poured. into a potassium iodide solution and the solution diluted to 300 ccs. with water. A small amount of benzene was added when the dye crystallised. The dyestufi was recrystallised from methyl alcohol and considered of golden crystals, melting, at C. with decomposition.

The product; is a valuable sensitising dyestufli. Incorporated in a silver bromide. emulsion it imparts a range of sensitivity between 6700 and 8300 A with a maximum at about noon.

Example II 0.75 gm. of 1-methylbenzthiazole and; 0.95 gm. of methyl-p-toluene sulphonate were mixed together and fused at 140 C. for three hours. The product was then dissolved in 40 ccs. of absolute alcohol, and 0.28 gm. offused sodium acetate and 3.4 gms. of diformyl-acetone-hexa-ethyl-acetal added to the hot solution. The mixture was then heated to boiling and then allowed to cool for about five minutes. During this treatment a bright blue-green colour developed. The solu- The product is a valuable sensitising dyestuif.

Incorporated in a silver bromide emulsion it imparts a range of sensitivity between 7200 and- 8150 A with a maximum at about 7700 A.

Example III 1 I 0.5 gm. of l-methyl-5:6-benzbenzthiazole and 0.5 gm. of ethyl-p-toluene sulphonate were mixed together and fused at 140-160 C. for four-and-ahalf hours. The mixture was then cooled and refluxed with cos. of pyridine. The mixture was then allowed to cool down to 100 C. and 1.77 gm of diformyl-acetone-hexa-ethyl-acetal added. The mixture was then warmed on a water bath and after about three minutes an intense green colour developed. The mixture wasthen poured into a potassium iodide solution. The dyestuff crystallised out on cooling and was separated by filtration. The dyestuif was washed with warm water, ethyl alcohol and hot benzene and then recrystallised from ethyl alcohol. The product consisted of crystals which gave a bright green solution in ethyl alcohol and which melted at 207 C. with decomposition. The product is a valuable sensitizing dyestufi. Incorporated in a silver bromide emulsion it imparts a, range of sensitivity between 7500 and 8400 A with a maximum at about 8100 A.

I claim:

1. Process for the preparation of tricarbocyanine dyestuffs which comprises condensing, in the presence of a solvent and an acid binding agent, a compound of the general formula:

where X is the residue of a heterocyclic nucleus selected from .the group consisting of the thiazole, selenazole, aryl thiazole and aryl selenazole nuclei, Y is the negative radical of an acid and R is a. group selected from the group consisting of alkyl and aralkyl groups, with a compound of the general formula:

where R1 is an alkyl group. 7

2. Process according to claim 1 wherein X constitutes the atoms necessary to complete with the nitrogen atom a benzthiazole nucleus.

3. Process according to claim 1 wherein R is a lower alkyl group.

4. Process according to claim 1 wherein R1 is an ethyl group.

5. A dyestuff of the general formula:

wherein X is the residue of a heterocyclic nucleus selected from the group consisting of the thiazole, selenazole, aryl thiazole and aryl selenazole nuclei, Y is the negative radical of an acid, R is o a group selected from the group consisting of alkyl and aralkyl groups and R1 is an alkyl group.

6. A dyestufi of the general formula:

wherein Y is the negative radical of an acid, R is a group selected from the group consisting of alkyl and aralkyl groups and R1 is an alkyl group.

7. A dyestufi' of the general formula: S

wherein Y is the negative radical of an acid, R is a lower alkyl group and R1 is a lower alkyl group.

8. A dyestuff of the general formula:

-oH=oH-cH=o-c11=oH-crr=o 0 ooze. R/ \Y I t wherein Y is the negative radical of an acid and R is a lower alkyl group.

9. A dyestuff of the general formula:

C-OH=OHCH=CCH=CHCH=C N/ 02H: N

I/ .\O2H5 lzHs 10. A dyestuff of the general formula: 

